With the increasing demand of packaging perishable goods for consumption, such as meat and dairy products, medicinal and cosmetic products in reclosable containers, it is advantageous to devise a packaging which is substantially less expensive than the standard glass jar with threaded cap and the like. Reusable plastic containers are suitable for this type of packaging because they are inexpensive to manufacture on a high speed basis, the plastic from the forming process is recyclable and the package, as waste, is recyclable.
Available on the market are plastic containers for perishable goods; however, the lids therefor which provide the hermetic seal on the container to maintain the freshness of the goods is usually not reusable. It is common, for example, to find a plastic container with an aluminum foil lid heat-sealed thereto to maintain the freshness of the product. Such foil is torn off the container leaving unsightly portions of foil on the container rim. An additional lid is usually provided with the container for reclosure of the container. Such a package is complex and results in wastage of the foil which is not reusable and adds costs to the package in terms of the required additional lid.
It is, therefore, desirable in packaging perishable goods to provide a container with a lid therefor which provides a hermetic seal and yet is reusable. The lid has a circumferential area which is heat-sealed to the container rim and another portion remote therefrom, which, in cooperating with a complementary portion on the container, provides for the reclosure of the container. In addition, the package, as heat-sealed, must be readily opened when it is desired to remove the heat-sealed lid from the container. Solvent-based types of adhesives have been used in providing a seal between lid and container. There are, however, several drawbacks in the use of solvent-based adhesives, such as the extended drying ovens required to remove the solvent from the applied adhesive and the problem of solvent recovery to prevent air pollution.
Other existing processes for providing layers of adhesive on lids have other drawbacks due to their complexity in application of adhesives to the substrate and the extended processing times required in forming lids for containers. Formed lids may be subsequently coated with solvent-based adhesives; however, due to to irregular shape of formed lids, there is usually an uneven layer of adhesive applied to the lid.
The reusable plastic container and plastic lid therefor and processes for making same of this invention overcome the above-identified drawbacks. The lids are readily manufactured on a high speed basis and are readily heat-sealed to containers. On reopening the heat-sealed container, the set adhesive is removed from the container rim. The process for coating the container rim with adhesive substantially reduces the amount of adhesive used and, therefore, cuts manufacturing costs.